Self-priming axial-flow pump



Dec. 29, 1964 J, RICHARDS 3,163,120

SELF-PRIMING AXIAL-FLOW PUMP Filed May 18, 1962 FIG.|

0000000 0000 o o 0000 on amp /0 o 150E110 oooqgb 0000 oo o ooeo 00 I7uoooooo 0000000: o 0000 no 3 Sheets-Sheet l JOHN F). RICHHRDS ATTORNEYSDec. 29, 1964 J. A. RICHARDS 3,163,120

SELF-PRIMING AXIAL-FLOW PUMP Filed May 18, 1962 3 Sheets-Sheet 2 F'IG.7

FIG. 3

INVENTOR. JO/WV I). R/Cf/HRDS #M ATTORNEYS Dec. 29, 1964 J. A. RICHARDS3,163,120

SELF-PRIMING AXIAL-FLOW PUMP Filed May 18, 1962 3 Sheets-Sheet 3 a FIG.4

I '1;I I 42 I N VEN TOR. JOHN H. RICK/HROS ATTORNEYS United StatesPatent insane Patented Dec. 29, 1964 3,163,126 SELEPRIIWING AXIAL-FLGWPUMP John A. Richards, Seattle, Wash, assignor to fiascade ManufacturingCompany, Portland, Greg, a corporation of Qregon Filed May 18, 1962,Ser. No. 196,577 7 Claims. (Cl. 103-113) This invention relates toliquid pumps of the axial flow character. Pumps which are referred to asaxial flow pumps can be either single or multiple stage; and may employseveral types of prime movers, or impellers as they will be hereinaftertermed. These several types can be classified as falling into fourgeneral categories:

(1) Propeller pumps (2) Mixed flow pumps, in which the impeller ispartly centrifugal and partly screw (3) Open impeller turbines, thesebeing centrifugal pumps with parts arranged in a manner which allows foraxial flow (4) Closed impeller pumps, much the same as the open typeexcepting that both sides of the impeller are shrouded.

A characteristic of axial flow pumps is that the impeller must be keptflooded, wherefor on the occasion of each start-up, on an installationwhere the impeller is called upon to lift liquid from a source thereofwhich lies at a level below the level occupied by the impeller of thepump, it becomes necessary to prime the pump.

The present invention has for its general object the provision of anaxial-flow pump incorporating in its design means by which the pump ismade self-priming.

This and other more particular objects and advantages will appear and beunderstood in the course of the following description and claims, theinvention consisting in the novel construction and in the adaptation andcombination of parts hereinafter described and claimed.

In the accompanying drawings:

FIGURE 1 is a fragmentary longitudinal vertical sectional viewillustrating one type of an axial-flow pump embodying preferredteachings of the present invention.

FIG. 2 is a fragmentary horizontal sectional view thereof on line 22 ofFIG. 1.

FIG. 3 is an exploded view of parts of the pump ineluding theimprovements of the present invention.

FIG. 4 is a fragmentary vertical sectional view illus trating anothertype of axial-flow pump embodying improvements of the present invention.

FIG. 5 is a horizontal sectional view on line 5-5 of FIG. 4.

FIGS. 6, 7 and 8 are diagrammatic views showing salient flow patterns;and

FIG. 9 is a fragmentary longitudinal vertical sectional viewillustrating a modified self-priming version of an axial-flow pump ofthe type shown in FIG. 1, employing a reduced scale.

First describing the embodiment of FIGS. 1 through 3, there is shown apump casing It) formed in its lower portion with a horizontal pumpcylinder 11. The suction end of this cylinder is denoted by 12. Water orother liquid which is to be pumped is drawn through a suction pipe 16into an ingress chamber 14 occupying a level above the pump cylinder. Aflap valve 15 normally closes the outlet from this chamber. Betweenchambers 14 and 12 is a screening basket 17. A rotary impeller of thepropeller type works in cylinder 11. Illustrated as a 3- stage impeller,the propellers are carried by a shaft 21 driven from an electric motor22, and have the usual stationary diffusers 23 provided at the suctionside of each propeller.

Journaled by its inner or front end on a bearing which is carried by adowel pin 24, the propeller shaft 2 1 has its outer or aft end attachedby a shear pin 25 to the armature shaft 2.6 of the motor. Such armatureshaft is received through a sealing muff 27, and giving support to themuff is an adapter head 28 which fits in the after end of the pumpingcylinder. This adapter head is axially spaced a rather substantialdistance beyond the final propeller of the multi-stage series. Above thepropeller shaft a baffle plate 30 occupies this space, being madeintegral with the head and lying radial to the propeller shaft in thelongitudinal vertical plane of the shaft axis. Below the propeller shaftthe head is desirably formed with a protruding toe portion 31 having aconcave profile configuration when viewed from the side.

Water being pumped travels upwardly from the propeller chamber past thebaffle plate to a discharge pipe 32. The proper length of the baffleplate, considered in a direction endwise to the travel path of thepumped water, will vary as between axial-flow pumps of differingdesigns. In the instance of the illustrated pump I find it desirable toprovide a baffle plate of considerable length. To this end I providewithin the pump casing a vertical discharge passage 33 lying in anintervening position between the bafile plate 30 and the discharge pipe32. The longitudinal vertical plane occupied by the baffle platecoincides with a diameter of this passage, and at opposite sides of thepassage, on this diameter, grooves 34 are let into the walls of thepassage. A plate 35 fits in these grooves to produce a co-planarprolongation of the baffle plate. I have shown such prolongation asbeing perforated with multiple through-holes 36 of small diameter. Ithas been found that the bafile plateby which term I include both of theplates 3% and 35rnay be solid or may be either slotted or perforated inwhole or in part. It is pointed out in this regard that it is onlythrough experimentation that I have been so far enabled to determine themost effective pattern for any'given designof pump.

The functioning of the baflle plate will be best understood by pointingout that when an axial-flow pump is started the major portion of thepriming fluid carries to the discharge side of the final impeller andthen tends to rotate with the impeller. This is the case even though thepump may have a final diffuser, or straightener, located behind thefinal impeller, in that the diffusers of an axial flow pump have a shortlength measured along the direction of flow. Air from the suction sideof the impeller becomes mixed with the priming fluid and by the rapidrotation of the mixture a centrifugal force is created. The liquidportion of this mixture, being more dense, tends to be driven to theoutside, leaving the less dense air portion toward the center. My baffleplate, as one of its accomplishments, breaks up the centrifugal actionand thereby obtains a more uniform mixture within the propeller chamber,with the net result that there is a higher percentage of the air at theoutside of the mixture. The air is thus enabled to more readily escapethrough the discharge opening. A further accomplishment takes place asfollows: the driving force of the impeller as it acts upon theair-liquid mixture imparts energy to the latter. Due to the plates closeproximity to the shaft and to the surrounding wall the plate acts as adiverter and, depending on the shape, size, and placement of the plate,forces the mixture to leave the vicinity of the impeller and either passthrough the perforations or over the edge which is distal to theimpeller, in consequence of which the mixture leaves the highlyturbulent impeller area and reaches a relatively calm zone containingliquid which is relatively free of air. The velocity of the mixturerapidly drops off as it passes through the near-static liquid and theforce of gravity now overcomes other forces involved and a portion ofthe air leaves the mixture and escapes through the discharge opening. Noprimary fluid has been lost in this operation, and the described actionof combining air from the suction side of the impeller with fluid on thedischarge side, and moving this mixture from a zone of turbulence to onerelatively free of such turbulence, with contained air escaping in theprocess, continues. The pump functions as an air pump until all air hasbeen removed between the impeller and the source of liquid supply.

The above is a rather general summation of the priming result which Iattain. In FIGS. 6, 7 and 8 I have diagrammed the motion pattern towhich air and liquid is subject in the pump of the present invention asit moves between the suction chamber 12 lying at the front end and thedischarge chamber 29 lying at the after end of the impeller.

During priming the pressure on the suction side is reduced, and apressure difierential between the discharge and suction chamber iscreated. This diiierential varies from 'zero pressure, at the start ofpriming, to ceiling pressure occurring just before actual pumping ofliquid takes place. This ceiling pressure will vary from installation toinstallation, and is a function of suction height and the pressure atthe discharge.

Separating the suction from the discharge is a liquid seal. Created bythe dynamic action of the impellers the liquid in this seal isrepresented in FIG. 6 by the arrows which surround the drive shaft, androtates at very nearly the same speed as the impeller. In addition tothis rotation a second circular motion is created. FIGS. 7 and 8 viewthe impeller from the side, and shown by these views are rotationpatterns under two conditions, that of 7 being a condition in which nopressure difference exists between the suction and discharge side of theimpeller, and that of 8 being a condition in which a pressure differenceobtains. The x x axis lies at the longitudinal cenier of the impeller inthe former instance, and tilts to the side of higher pressure in thelatter instance. The change of pressure increases the circulation on thelowpressur'e' side. Thislurihalance in circulation creates a force-fieldwhich counteracts'the pressureforces. While for illustrative purposesthe rotation with the impeller (FIG. 6) and the circulation within theimpeller (FIGS. 7 and 8) are shown separately, the two motions actuallyare simultaneous. The absolute path of the fluid particles can best bedescribed as a circular cork screw. A factor which must be recognized asaffecting the degree of tilt of said axis is the density of the pumpage.The pumpage is a mixture of liquid and gas, and since gas iscompressible the density is not only a function of the amount of gas butalso the pressure at the location considered. The significance of saiddensity factor is simply that on a multi-stage pump each pumping unit ofthe impeller has a different vortex pattern. '7

During the priming cycle the air in the suction line and suction chamberis evacuated by moving it through the liquid seal into the dischargechamber and out the discharge line. The liquid seal as such does nottransport any gases from suction to discharge since the circulationsdescribed are confined to each pumping unit of a multi-stage impeller. V

The above is an over-simplified description of the real flow pattern. Ivisualize each individual liquid particle as having only a localizedtravel, moving a short distance toward the discharge and there releasingpart of the gas to other liquid particles and then returning toward thesuction side. A chain reaction of this nature will give much the sameeffect as the simplified circulation described. The straightener lipsalso create pulsations. These shock waves are feasibly beneficial forpriming.

It should perhaps be again stressed that the accomplishments of thebaffle plate are to (I) produce a discharge chamber of reducedturbulence so that the gas will separateffrom the liquid, (2) direct theseparated gas into the discharge pipe, and (3) prevent the gas frombecoming trapped or from being returned to the impeller.

It should be here pointed out that the air need not be dischargedthrough the pumps normal discharge opening. Should such normal dischargeopening be directed downwardly, as is the case with some horizontalpumps, a separate opening for escape of air can be provided on the upperside of the pump casing. Such an escape opening can likewise be providedon vertical pumps in which the normal discharge turns abruptly downward.in either such case, for automatic operation, it is only necessary thatmeans such as a float or a pressureresponsive check valve be provided tocause the air-vent opening to close when the prime has been made. FIG. 9illustrates teachings of the present invention applied to a horizontalpump of the above-mentioned type having its discharge opening directeddownwardly, and indicating the manner in which an air-escape check valveis applied. Such check valve, denoted by (it), is set so as to close inresponse to a rise of pressure at the discharge or pressure side of thepump to a predetermined level (this being the ascertained ceilingpressure hereinabove referred to) and is or may be fitted with aregulating control handle 61. The discharge pipe 32' has a U-bend toproduce a trap in which air-free liquid collects during the pumpsself-priming action. The pump casing is denoted by 1%, and functioningcounterparts of the plates 30 and 35 are denoted by 33' and 35respectively.

In FIGS. 4 and 5 I have shown a vertical-type axialfiow pump equippedwith a bafile plate embodying teachings of the present invention. Thepump is shown as e-ing equipped with a single-stage propeller 4t) andpairs of diametrically opposed ditfusion vanes, as 41-42 and 43-44,above and below such propeller. The lineshaft 45 which drives thepropeller from a top-mounted motor (not shown) is enclosed in a shafttube 46 occupying a position axial to a discharge column 47. Along-radius discharge elbow 48 extends laterally from the upper end ofthe discharge column in the vertical plane occupied by the diliuservanes. The bathe plate, designated by 50, is applied as a co-planarprolongation of the one of said upper vanes which extends radially fromthe shaft tube 4d on the same side as that occupied by the dischargeelbow. Some vertical-pump designs might dictate that this hafile beextended beyond the discharge column into the throat of the dischargeelbow.

A vertical pump employing the bafile plate of the present invention mustbe so designed that, when stopped, a body of priming liquid will beretained in the casing in a position to be picked up by the impellerwhen the pump is again started up. This can be accomplished in a numberof ways as, for example, by forming a U-trap in the suction pipe 51.

A feature of the present invention which is highly important is that thepump will not lose prime should gas enter the suction line. The pumpclears its passages automatically and resumes delivery of the pumpedliquid.

It is believed that the invention will have been clearly understood fromthe foregoing description of the illustrated embodiments. Changes in thedetails of construction may be resorted to without departing from thespirit of the invention and it is accordingly my intention that nolimitations be implied and that the hereto annexed claims be given thebroadest interpretation to which the employed language fairly admits.

What I claim is:

1. In combination with the rotary impeller of an axialflow pump, and acasing housing said impeller formed so that a body of the liquid to bepumped is at all times available to the impeller as a prime for thepump: a stationary diverter contained within the casing in a dischargepassage travclled by pumped liquid as the latter initially leaves thedischarge end of the impeller and formed so as to (l) interruptimpeller-induced centrifugal motion of a fluid composed of said primingliquid mixed with air drawn by the impeller from the suction side of thepump and (2) lead said mixture to a zone relatively free ofimpeller-induced turbulence occupying a level no lower than thedischarge end of the impeller and from which the contained air is freeto escape by ascension.

2. Structure according to claim 1 in which said diverter extends for adistance along said passage suflicient in length to substantiallyisolate said zone from the turbulence imposed by the impeller upon theliquid-air mixture.

3. Structure according to claim 2 in which the diverter is in the natureof a baflie plate extending into approximate touching contact with thewall of the passage on a diameter of the latter.

4. In an axial-flow pump, a rotary impeller mounted to turn about ahorizontal axis, a pump casing housing said impeller providing inflowand outflow passages to and from the impeller, said outflow passageincluding a vertical section rising to a height elevated above thechamber in which the impeller Works and connecting with said chamber byan elbow section, and a stationary diverter serving a bafiie functionupon a liquid-air mixture driven by the impeller and comprising a plateoccupying a diameter of the vertical section co-planar with a diameterof the impeller chamber, said plate depending from the vertical sectionthrough approximately the upper onehalf of the elbow section and at itsleading edge extending into such close proximity of the impeller as tointerrupt centrifugal motion of liquid-air mixture leaving the dischargeend of the impeller.

5. The axial-low pump of claim 4 in which said plate is perforated atleast in part.

6. The axial-flow pump of claim 4 in which the plate is imperforateother than for a portion thereof which lies in such distal relation tothe impeller as to be outside a zone of turbulence reflecting saidcentrifugal motion of the liquid-air mixture.

7. In an axial-flow pump, a rotary impeller mounted to turn about avertical axis, a pump casing housing said impeller providing an inflowpassage to the lower end of the impeller and an outflow passage from theupper end of the impeller, a vertical drive shaft to the impellerdisposed centrally of the outflow passage, and a baffle plate occupyingthe space between the shaft and the outer wall of the outflow passage ona radius of the former and extending upwardly into said outflow passagefrom approximately the upper end of the impeller, the baflie platehaving considerable length measured along the axis of the shaft, meansbeing provided by which a body of liquid to be pumped is at all timesavailable to the impeller as a prime for the pump.

References Cited in the file of this patent UNITED STATES PATENTS2,375,571 Mann May 8, 1945 2,428,487 Fernstrum Oct. 7, 1947 2,461,925Rupp Feb. 15, 1949 2,627,812 Mann Feb. 10, 1953. 2,627,817 Mann et alFeb. 10, 1953 2,934,021 Conery et a1 Apr. 26, 1960 2,945,448 FrederickJuly 19, 1960 FOREIGN PATENTS 601,653 Great Britain May 11, 1948

1. IN COMBINATION WITH THE ROTARY IMPELLER OF AN AXIALFLOW PUMP, AND ACASING HOUSING SAID IMPELLER FORMED SO THAT A BODY OF THE LIQUID TO BEPUMPED IS AT ALL TIMES AVAILABLE TO THE IMPELLER AS A PRIME FOR THEPUMP: A STATIONARY DIVERTER CONTAINED WITHIN THE CASING IN A DISCHARGEPASSAGE TRAVELLED BY PUMPED LIQUID AS THE LATTER INITIALLY LEAVES THEDISCHARGE END OF THE IMPELLER AND FORMED SO AS TO (1) INTERRUPTIMPELLER-INDUCED CENTRIFUGAL MOTION OF A FLUID COMPOSED OF SAID PRIMINGLIQUID MIXED WITH AIR DRAWN BY THE IMPELLER FROM THE SUCTION SIDE OF THEPUMP AND (2) LEAD SAID MIXTURE TO A ZONE RELATIVELY FREE OFIMPELLER-INDUCED TURBULENCE OCCUPYING A LEVEL NO LOWER THAN THEDISCHARGE END OF THE IMPELLER AND FROM WHICH THE CONTAINED AIR IS FREETO ESCAPE BY ASCENSION.